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Expanded polystyrene foam, a packaging material, is traditionally injection-moulded by classical moulding techniques. However, the design and fabrication of these moulds is both intricate and time-consuming. In today's manufacturing environment of short time-to-market, the luxury of producing a mould for, often, a first-off article for client approval, is virtually untenable. Rapid prototyping technologies appear to offer an alternative method of fabrication which promises to drastically reduce the time for mould fabrication. When rapid prototyping of the mould is combined with microwave curing of the polystyrene, as an alternative source of energy to traditional steam heating, the benefit of considerably short throughput times can be expected. This paper describes the computer-integrated design and fabrication of both the mould and foam product, and discusses the main issues associated with rapid prototyping the mould, viz. accuracy of the prototype mould and the suitability of acrylic resin used in stereolithography apparatus for fabricating the mould, as well as the parameters for moulding expanded polystyrene using microwave energy. Initial results suggest that both the stereolithography process, and the acrylic resin used to build the stereolithographic model, can be used for rapid prototyping expanded foam products and their associated mould. [ABSTRACT FROM AUTHOR]

The most commonly used input to a rapid prototyping (RP) system is the de facto stereolithography file (STL). Several problems plague these STL files owing to the very nature of STL files and the non-robustness of commercial CAD system model tessellators. The consequences of not correcting these errors are detrimental to the creation of the intended prototype. These are highlighted in the paper. In Part 1 of two papers, a description of all STL-files-related errors is given. The paper also proposed a generic solution to solve one of the major problems in the proper creation of a prototype, that is, the problem of missing facets. Part 2 deals with special cases of errors associated with the STL files. The performance evaluation of the proposed solution is also given. [ABSTRACT FROM AUTHOR]

The most commonly used input to a rapid prototyping (RP) system is the de facto stereolithography file (STL). Several problems plague these STL files owing to the very nature of STL files and the non-robustness of commercial CAD system model tessellators. The consequences of not correcting these errors are detrimental to the creation of the intended prototype. These are highlighted in the paper. In Part 1 of two papers, a description of all STL-files-related errors is given. The paper also proposes a generic solution to solve one of the major problems in the proper creation of a prototype, that is, the problem of missing facets. Part 2 deals with special cases of errors associated with the STL files. The performance evaluation of the proposed solution is also given. [ABSTRACT FROM AUTHOR]

Rapid prototyping processes produce parts layer by layer directly from the CAD model. The processes proceed by first slicing the geometric model of a part into layers. A standard interface is necessary to convey varied geometric descriptions from numerous CAD packages to Rapid Prototyping (RP) systems. The STL (STereoLithography) format is the most commonly used interface for this purpose. Unfortunately, it is an approximate model and is frequently not robust. Therefore, other interfaces are proposed to be used for RP systems. This paper, Part 1, will discuss several existing interfaces including the STL file for the RP systems. The strengths and weaknesses of these formats when used for RP systems are analysed. Furthermore, a new improved format is proposed by the authors in Part 2. In that paper, the design considerations and data structure of the new format are introduced. [ABSTRACT FROM AUTHOR]

The STL (STereoLithography) file format, as developed by 3D Systems, has been widely used by most Rapid Prototyping (RP) systems and is supported by all major computer-aided design (CAD) systems. However, it is necessary to improve the STL format to meet the development needs of RP technologies. In Part 1, several existing and proposed formats have been discussed. This paper, Part 2, will present an improved interface between CAD and RP systems. The new interface is a file format that supports the STL format, removes redundant information in the STL format and adds topological information to balance storage and processing cost. In addition to supporting facet boundary models, the new interface supports precise models by using the edge-based boundary representation. This paper discusses the design considerations of the new interface and data structures for both facet models and precise models. Finally, a comparison of the new interface and the STL file format will be made. [ABSTRACT FROM AUTHOR]

This study is carried out to develop a direct link between a laser digitiser and a rapid prototyping system for biomedical applications. Two CAD/CAM systems, DUCT and Pro-Engineer, are investigated and the DUCT system is found to be more suitable for this purpose. A laser digitiser is used to capture three-dimensional surface data for the object. With the aid of the CAD/CAM system, the data can be manipulated in a number of ways for display, modification and enhancement. In addition, the object scanned by the laser digitiser can be physically produced relatively quickly and accurately using StereoLithography Apparatus (SLA), a leading rapid prototyping system. Feasible and practical solutions to the problems encountered in the CAD surface model construction are proposed and illustrated. Two case studies, a facial and a breast model, are presented. Results show that this integrated approach can be applied effectively in the biomedical field. [ABSTRACT FROM AUTHOR]

Each rapid prototyping (RP) process has its special and unique advantages and disadvantages. The paper presents a state-of-the-art study of RP technologies and classifies broadly all the different types of rapid prototyping methods. Subsequently, the fundamental principles and technological limitations of different methods of RP are closely examined. A comparison of the present and ultimate performance of the rapid prototyping processes is made so as to highlight the possibility of future improvements for a new generation of RP systems. [ABSTRACT FROM AUTHOR]

Rapid Prototyping (RP) is a technology for rapid computerised building of 3D physical parts. It can be defined as an automated and patternless process which allows solid physical parts to be made directly from computer data in a short time. RP acts as the “manufacturing middle” to link up the computer-aided design (CAD) process and manufacturing processes. It includes the making of prototypes for design verification and even the making of tooling for production. With the trend towards concurrent engineering and the widespread use of CAD, RP has quickly become a booming business in the past few years. This paper presents an overview of the implementation of RP technology in Hong Kong and the critical decision factors in implementing RP in the Hong Kong manufacturing industry. [ABSTRACT FROM AUTHOR]

Connectors are developed to satisfy the needs of advanced technology in telecommunication switching systems and companies have several products designed to fulfil the needs of the many switching networks available. The “Four-wall-header” is one such product from one company. The traditional manufacturing line relies heavily on hard tooling which is both expensive and time-consuming. This paper presents an alternative method of integrating rapid prototyping technologies, in particular, stereolithography apparatus (SLA), with a vacuum casting system to produce a wide range of polyurethane parts. Altogether, three approaches are analysed and evaluated for making the moulds: rapid pattern, rapid tooling and a hybrid approach. [ABSTRACT FROM AUTHOR]

In recent years, new surgical techniques have been developed to improve the quality of operations, reduce the risk to patients and reduce the pain experienced by patients. Prominent developments include minimally invasive surgery, robot-assisted hip operations, computer-assisted surgery (CAS) and virtual reality (VR). These developments have helped surgeons operate under difficult visual conditions. Rapid prototyping (RP) technology has also found applications in medicine. The RP technique is able to fabricate a representative, physical 3D model. This 3D model can enhance interpretation, visual and physical evaluation, and the rehearsal and planning of the surgical steps before a surgical operation is carried out in order to eradicate the trauma. This paper presents the procedures involved in the conversion of computerised tomography (CT) scan data to a useful physical model. A case study of a CT scanned file of a patient who had an injury to the right eye socket is presented. Three different RP systems (SLA, SGC and LOM) are benchmarked for comparison in terms of the surface finish, accuracies, visual appearance and processing speed. Because of the ability of RP to fabricate models that are complex in design with intricate features that may be hidden by undercuts, as demonstrated in this paper, the results of this research can be extended to applications in general engineering. One specific area of application would be reverse engineering. [ABSTRACT FROM AUTHOR]

Rapid prototyping has gained wide industrial acceptance in recent years. Its main advantage is that it improves the “time to market” and the design quality of a product. Most rapid prototyping processes have to build the solid volume layer by layer. The tracing of the cross-sectional area in each layer is the most time-consuming step. The process can be speeded up if the material volume to be traced can be reduced by extracting some empty volumes in the original solid. However, the hollow solid generated by employing the negative solid offset technique is subject to the problem of no interior support. In this paper, a sub-boundary octree approach of generating thin shell solids with reinforced interior structuring is proposed. The procedures to generate a reinforced thin shell solid are studied. Various testing models are produced by a fused deposition modelling rapid prototyper and the results are supportive. [ABSTRACT FROM AUTHOR]

Geometric accuracy of components is one of the most important quality characteristics in layered manufacturing processes on which most rapid prototyping (RP) techniques are based. Layered manufacturing is an approximate fabricating process in which the final geometric error of the physical part is affected, not only by the approximation technique used, but also by the fabrication process. Errors that occur in one layer could propagate and transfer to other layers causing an accumulated error effect in the process. In this paper, a concept of disturbance error is introduced to describe the effect of accumulated errors in the fabrication process. A physical model is presented to describe error interactions and error transfer mechanisms in the layered manufacturing process. A geometrical model is developed using surface approximation techniques to describe the relationships of the geometrical errors. It is shown that although the complexity of the part geometry is not directly related to the manufacturing process, it will affect the geometrical errors of the part produced. [ABSTRACT FROM AUTHOR]

Layered manufacturing based rapid prototyping processes are subjected to not only a staircase effect owing to the approximating process used, but also an accumulated error transfer between layers. Certain types of error such as surface tilting and layer thickness variations that occur in one layer can transfer to other layers above it. This paper describes a mathematical model based on the physical and geometrical models discussed in Part 1 of the paper. The model uses the matrix transformation method to analyse the effect of transformation of local errors to the multiple layer global errors. A data preparation error transformation matrix is used to describe the error interactions between layers during the data preparation stage. A disturbance error transformation matrix is used to describe the error interaction within each layer and error propagation between layers during the part building process. This model describes geometrical error analysis involving profiling error, layer inclination and layer thickness variations. Numerical evaluation of the model is carried out for a typical benchmark component. [ABSTRACT FROM AUTHOR]

Prototypes of a design are always needed for the purposes of visualisation and evaluation for manufacturability, functionality, and aesthetic appearance. Since the prototyping process requires a significant amount of cost and time, various rapid prototyping processes have recently been introduced. However, it is usually necessary for a part built up by a rapid prototyping system to be finished by a post-processing process, in which the stair steps on the surfaces, the support structures (if they exist), and the unprocessed material are eliminated. This post-processing is usually done manually and is a time-consuming task. Eliminating the trapped volumes (the volume of the unprocessed material entrapped by the solidified portion) is sometimes impossible in some processes. This study provides a designer with a tool to detect the existence of trapped volumes and to calculate the quantity in a given build-up direction, so that a suitable build-up direction is chosen or the part is built in pieces to avoid the problems caused by the trapped volumes. Since the proposed algorithm can efficiently calculate the amount of the trapped volumes in any build-up direction, it has the potential for such applications as optimising the build-up direction to minimise the trapped volumes. [ABSTRACT FROM AUTHOR]

Rapid prototyping (RP) is the production of a physical model from a computer model without the need for any jig or fixture or numerically controlled (NC) programming. This technology has also been referred to as layer manufacturing, material deposit manufacturing, material addition manufacturing, solid freeform manufacturing and three-dimensional printing. In the last decade, a number of RP techniques has been developed. These techniques use different approaches or materials in producing prototypes and they give varying shrinkage, surface finish and accuracy. Virtual prototyping (VP) is the analysis and simulation carried out on a fully developed computer model, therefore performing the same tests as those on the physical prototypes. It is also sometimes referred to as computer-aided engineering (CAE) or engineering analysis simulation. This paper describes a comparative study of the two prototyping technologies with respect to their relevance in product design and manufacture. The study investigates the suitability and effectiveness of both technologies in the various aspects of prototyping, which is part and parcel of an overall design and manufacturing cycle. [ABSTRACT FROM AUTHOR]

Rapid tooling (RT) is the technology that adopts rapid prototyping (RP) techniques and applies them to tool and die making. Research into RT techniques has shown that it is gaining more importance and is starting to pose a serious threat to conventional machining. In this paper, several popular RT techniques are discussed and then classified. A comparison is also made on these techniques based on tool life, tool development time and cost of tool development. [ABSTRACT FROM AUTHOR]

A new approach to remove point data with Delaunay triangulation is introduced to deal with the size problems of the STL file and the difficulties in the operation of the rapid prototyping (RP) process. The selection of a group of triangles, based on the angle, is used for a robust and reliable implementation of the Delaunay triangulation method. The developed software enables the user to specify the criteria for the selection of the group of triangles by the angle between triangles, the percentage of reduced triangles, and the allowable area. This approach can be used to reduce the measuring data from the laser scanner, thus save the handling time of point data during the modelling process and is useful for verifying and slicing the STL model during the RP process. [ABSTRACT FROM AUTHOR]

In this paper, Part 2, the emphasis is on a secondary powder deposition method, which is an electrostatic technique based on electrography. Developed toner on the photoconductor is scraped off using mechanical shearing and is deposited using an electrostatic force by electroplating. Results have shown that by reducing the distance between the photoconductor and surface of deposition, the resolution of the printout can be refined. Other important factors include the efficiency of powder removal from the photoconductor, printing speed, and the traversing speed during deposition. [ABSTRACT FROM AUTHOR]

PROTOTYPES, COMPUTER-aided design, COMPUTERS in engineering, INTERNET, WIDE area networks, and ENGINEERING design

The STL file, which is de facto standard for the rapid prototyping industries, has too large a file size. This paper proposes an improved interface between CAD and rapid prototyping systems, i.e. a CS (compressed STL) file that has very low data storage redundancies and is completely compatible with the STL file. The CS file is about a quarter of the size of the original binary STL file, without any model information loss. This is very suitable for file transferring via the Internet. Removing coordinate data of duplicate vertices, bit-compression technology, and a comparison of the size and compressed performance of the STL and the CS are also discussed. [ABSTRACT FROM AUTHOR]

FLEXIBLE manufacturing systems, PETRI nets, MATERIAL requirements planning, PROCESS control systems, PRODUCTION engineering, and PRODUCTION scheduling

Manufacturing systems are faced with ever-increasing customisation and unstable demand. The traditional hierarchical control structures for shop floor (pre-release planning, scheduling, dispatching and activity control) are often inflexible in responding to unexpected scenario changes and are thus not robust to system disturbances. In this paper, an object-oriented approach to modelling of FMS dynamic tool allocation and control under a non-hierarchical shop floor control scheme using coloured Petri nets is presented. A client–server paradigm is used in the proposed modelling method. The complete FMS model is partitioned into individual classes (machines, magazines, tool transport system, SGVs, tool storage, etc.) thereby significantly reducing the complexity of the model to a tractable size. The system performance under different tool request selection rules is also evaluated using coloured Petri net simulation. The proposed method can provide the designer of a tool management system with a high-level and structured representation of the tool-sharing control. It also provides an effective method for prototyping and evaluating performance of object-oriented shop floor control software. [ABSTRACT FROM AUTHOR]

TURBINE blades, PROTOTYPES, ROTATIONAL motion (Rigid dynamics), EMBEDDED computer systems, ELECTRIC generators, ELECTRIC power, and FEASIBILITY studies

This paper presents the methodology for quantifying the blade assembly process with the future objective of fully automated assembly planning. The proposed method is aimed at eliminating the expensive and time-consuming physical prototyping needs by analysing and evaluating the feasibility of the blade assembly process using a CAD-based virtual prototype. The virtual prototype of the entire assembly operation is created for the blade assembly from a torque converter of an automobile transmission system. This model development is implemented using ProEngineer. Owing to the modelling requirements, the design intents, pertinent parameters, and their relationships in the entire blade assembly process must be captured and integrated into the model. The virtual assembly prototyping package developed is capable of computing and offering computer animated simulations of the interference of the blade tabs with the turbine and the pump shell during the assembly process. The work focuses on quantifying the blade assembly process by expertly defining some benchmarks and indices based on the kinematic behaviour of the assemblages. The benchmarks can also be used for documenting, evaluating, and comparing the blade assembly designs in various assemblages of torque converters to improve and transfer the experiences of the designers embedded in the model, for the torque converter industry. The model developed in this work has been tested and verified to be effective with a real torque converter model built at a local company. The results of the experiments are discussed. [ABSTRACT FROM AUTHOR]

TISSUE engineering, DESIGN, PROTOTYPES, POWDER metallurgy, CONCURRENT engineering, and MANUFACTURING processes

In tissue engineering (TE), a porous scaffold structure may be required as a template to guide the proliferation, growth and development of cells appropriately in three dimensions. Although TE scaffolds can be created using one of many conventional techniques available, most will suffer from a lack of mechanical strength and/or uniformity in pore distribution and sizes. This study is focused on creating scaffolds using rapid prototyping (RP) techniques. Utilising these novel techniques, a computer-aided design (CAD) of the scaffold structure must first be modelled. The scaffold structure is then fabricated directly from CAD data using a RP system. The objective of this research is to (1) investigate and select various polyhedral shapes suitable for scaffold modelling, (2) classify the selected unit cells, (3) create a parametric library of scaffold structures and (4) verify by building the CAD models using the selective laser sintering process. The first two objectives are covered in Part 1 of this two-part paper. The remaining objectives will be described and discussed in Part 2. [ABSTRACT FROM AUTHOR]

TISSUE engineering, PROTOTYPES, CONCURRENT engineering, FEASIBILITY studies, BIOMEDICAL engineering, COMPUTER-aided design, and MANUFACTURING processes

Rapid prototyping (RP) techniques have been found to be advantageous for tissue engineering (TE) scaffold fabrication due to their ability to address and overcome the problems of uncontrollable microstructure and the feasibility issues of complex three-dimensional structures found in conventional processing techniques. This research proposes a novel approach for TE scaffold manufacture using RP techniques. The approach involves the integration of medical imaging devices (CT/MRI) for the acquisition of anatomic structural data, three-dimensional CAD modelling for designing and creating the digital scaffold models and RP for fabricating the physical scaffolds. To aid the user in CAD modelling, a standard parametric library of scaffold structures is designed and developed. With the library, a user can select the geometry of the scaffold unit cell and size it to suit the end application of the TE scaffold. A developed application program will then assemble the scaffold structure from the selected unit cell, following the surface profile of the anatomic structure to be replicated. A physical scaffold will then be built using an RP system. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, RAPID tooling, MANUFACTURING processes, FLEXIBLE manufacturing systems, and SURFACE roughness

As the race to launch a product successfully into the market increases in speed, the drive to reduce metal tooling lead time will become more important. Time reduction for fabricating metal tools depends on fast, efficient, and flexible manufacturing processes that dramatically reduce lead times while not sacrificing mechanical properties. A novel process of rapid tooling, non-baking of ceramic moulding, was studied. It uses a casting mould made from ceramic slurry and rapid prototyping to form a metal tool. It provides a quick, accurate, and relatively cost-effective route for producing metal parts or tools. The process and key technologies are analysed in detail. The process has been used in the automotive, consumer products, casting, and toy industries. Applications show that the total costs for new products can be reduced by as much as 40–60%, and lead times can be reduced by 50–60%. The surface roughness is approximately Ra = 3.2, and it can be improved to better that Ra = 1.6 by polishing. The dimensional accuracy relative to size is about ±0.1 mm for dimensions less than 200 mm. [ABSTRACT FROM AUTHOR]

RAPID prototyping, NEW product development, PROTOTYPES, RAW materials, SHEAR waves, PHOTOPOLYMERIZATION, MANUFACTURING processes, and FINITE element method

Stereolithography is one of the rapid prototyping processes which uses a photopolymer as the raw material to build prototypes. The photopolymer absorbs energy by selective laser exposure. The curing effect starts when the absorbing energy exceeds a critical value, and the process is called photopolymerisation. The photopolymerisation changes the phase from liquid to solid. The cured volume can expand and then shrink on cooling. The process parameters such as the scanning speed, scanning path, scanning pitch, and the slicing thickness, lead to different shrinkage and curl distortion, so, the photopolymerisation process is a dynamic material behaviour. In this study, a dynamic finite element simulation code has been developed to simulate the photopolymerisation process. The simulated result for a suspended beam which corresponds to the process parameters shows that a short raster causes less curl distortion than a long raster. The experimental result agrees very well with the simulated result. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, NEW product development, COATING processes, MANUFACTURING processes, LARGE scale systems, and CONCURRENT engineering

Many technological difficulties exist in the field of rapid prototyping (RP) technology when making large-scale prototypes. The manufacturing efficiency is the main problem, and the process implemention and RP equipment also present difficulties. In this paper, the concept of divisional parallel scan is presented. Laminated object manufacturing (LOM) technology is used for the basic forming process and has been improved continuously through practice. Static divisional scan technology was also better developed to dynamic divisional scan technology, which can help in achieving the object of improving work efficiency and optimising design. [ABSTRACT FROM AUTHOR]

RAPID prototyping, NEW product development, COMPUTER-aided design, METAL spraying, METAL coating, MANUFACTURING processes, and CONCURRENT engineering

In order to build the complex built-in labyrinth design of an emitter which is a key element in water-saving devices, rapid prototyping and manufacturing (RP&M) is used to design the emitters and to manufacture corresponding rapid tooling (RT). Detailed CAD design of the emitter, CAD process design, and the generation of RT process modelling of the emitter have been carried out using parameterised design. Prototypes have been built using RP techniques to perform the rapid verification and modification of the emitter design; rapid tooling (RT) for the emitter has been fabricated using a metal spraying process to carry out trial-production. Finally, with the fabrication ofa precision mould as the basis, emitter mould design and manufacturing have been completed. As a result, the integration of design/verification/manufacturing of a mould and its products is realised. [ABSTRACT FROM AUTHOR]

LIQUID crystal displays, LIQUID crystal devices, NEW product development, MANUFACTURING processes, LITHOGRAPHY, RAPID prototyping, FINITE element method, and COMPUTER simulation

In many investigations, a liquid crystal display (LCD) has been used as the photo mask in a stereolithography system. The LCD mask has the potential to increase the speed of rapid prototyping (RP) fabrication as well as to reduce the system cost. Compared to the conventional laser-scanning technique used in 3D systems stereolithography apparatus (SLA), the reaction heat of layer curing is released as the area is exposed, and it is higher than that of the laser scanning in which the reaction heat only releases point-by-point. On the other hand, mask type stereolithography has a more serious shrinkage effect than the other methods and requires further analysis. This paper analyses the shrinkage deformation of the mask type stereolithography process. A simulation code based on the dynamic finite-element method has been developed to predict the 3D shrinkage and to monitor the RP fabrication, which consists of three stages of simulation which include the pre-processor, the analytic processor and the post-processor. In order to fabricate experimental parts, a mask type stereolithography system has been assembled. The principle of the experimental apparatus is also briefly described. For evaluation of the experimental and simulation results, a thin shell wall rectangular part was fabricated and measured. The simulation program developed has been proved to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

TESTING-machines, COORDINATE measuring machines, RAPID prototyping, REVERSE engineering, COMPUTER-aided design, PARAMETER estimation, and NUMERICAL analysis

One objective of this work is to determine the optimal combination of the probe diameter and grid distance for freeform surface measurement, and another is to determine the optimal parameters for the local Shepard interpolation. The optimal combination of the probe diameter and grid distance for freeform surface measurement was determined through a Taguchi matrix experiment. The smaller the probe diameter and grid distance, the better the accuracy of the surface normal based on the configured matrix experimental result. The optimal parameters, namely the exponent μ and the radius R, for the local Shepard interpolation were determined by using the minimisation method of the root-mean-square normalised error (RMSNE) between the measured data points and the theoretical data points on a standard steel ball surface. The optimal parameters determined were actually applied to the measurement of a freeform surface (mouse surface) on a coordinate measuring machine (CMM). The local Shepard interpolation method was used to interpolate 16 control points from 1054 measured data points. Bi-cubic Bezier- and B-spline surface CAD models were constructed through these interpolated control points. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, LASERS, INDUSTRIAL engineering, and MANUFACTURING processes

To meet the requirement of faster and precise slicing in rapid prototyping, a direct slicing approach from AutoCAD solid models is proposed. The sliced layers are saved in ASCII DXF files. Lines, arcs and circles are used to describe the section contours. This approach can be used in stereolithography, selective laser sintering, fused deposition modelling, and other rapid prototyping processes, e.g. laminated object manufactu-ing. [ABSTRACT FROM AUTHOR]

SIMULATION methods & models, MODELS & modelmaking, BOTTLENECKS (Manufacturing), PRODUCTION scheduling, MANAGEMENT, and THREE-dimensional imaging

Filling lines are too complex to allow realistic models of them to be evaluated analytically. In this paper, the requirements for designing filling lines are analysed, and a directed graph-based modelling formalism which unifies object oriented analysis methods, and the 3D geometry and mechanism required for the simulation is proposed. A framework of a virtual simulation system is proposed, and the architecture and main modules of the prototyping tool are introduced. These provide an integrated tool for the design and optimisation of filling lines. Entire facilities and filling line can be modelled in the modelling and simulation environment to evaluate alternatives, and to identify physical bottlenecks. An example is given. [ABSTRACT FROM AUTHOR]

SILICA sand, TEMPERATURE, CALCIUM, ALUMINUM, MAGNESIUM, and MELTING points

Silica sand is commonly used in the foundry industry. With a high melting point of 160°C, the silica sand is normally sintered in a high-temperature furnace. However, silica with contents of calcium, aluminium, magnesium, and chlorine, etc. can form low-melting point eutectics. Therefore, a relatively low-power laser can be used to sinter the silica sand directly. The investigation of the mechanism and process for direct laser sintering of the silica sand, without any binder, is presented in this paper. Combined with rapid prototyping (RP) technology, the laser sintering of the silica sand can be used to directly fabricate a sand casting mould, called a rapid sand casting mould. By avoiding the time-consuming process of fabricating a pattern, the rapid sand casting mould process has the potential of further reducing the lead time for producing a casting product. Some important issues, such as the lead time of producing a sand mould, its accuracy, and surface finish, etc., are discussed. [ABSTRACT FROM AUTHOR]

RAPID prototyping, NEW product development, MANUFACTURING processes, ASYNCHRONOUS transfer mode, SMALL business, TECHNOLOGICAL innovations, and INFORMATION resources management

Faced with today's competitive market, the development of innovative product needs to be accelerated. But this is limited by heterogeneous systems and a distributed environment. A way of utilising network technology to this end must be found. In this paper, we use a new approach, called asynchronous and synchronous coupling, which is a network-based product development approach. This is then applied to rapid-response manufacturing by small- and medium-sized enterprises in a distributed environment. It demonstrates integrated thinking, high development speed and a transparent development process. Visual technology and real-time monitoring technology are used to solve asynchronous process and data management problems. An ICE (integrated collaborative environment) is also created to support synchronous collaboration. [ABSTRACT FROM AUTHOR]

DESIGN, RAPID prototyping, INTERACTIVE computer systems, SURFACES (Technology), DEFORMATION of surfaces, COMPUTER-aided design, and MODELS & modelmaking

There is an increasing demand in conceptual design for more intuitive methods for creating and modifying freeform curves and surfaces in CAD modeling systems. The methods should be based not only on the change of the mathematical parameters but also on the user's specified constraints and shapes. This paper presents a new surface representation model for freeform surface deformation representation. The model is a combination of two functions: a displacement function and a function for representing an existing NURBS surface called a parent surface. Based on the surface model, the authors develop several novel deformation methods which are named SingleDef (Single-point constraint based deformation method), MultiDef (Multiple-points constraints based deformation method), CurDef (Curve constraints based deformation method) and FeatDef (Feature constraint based deformation method). The techniques for freeform surface deformation allow conceptual designers to modify a parent surface by directly applying point constraints, curve constraint or a surface constraint to the parent surface. The deformation methods are implemented in an experimental CAD system. The results show that designers can easily and intuitively control the surface shape. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, PRODUCTION engineering, MACHINING, RAPID prototyping, INDUSTRIAL engineering, ALLOYS, NEW product development, and METAL products

High-speed machining is known as one of the most effective rapid prototyping and/or manufacturing (RPM) processes that provides the various machining materials with excellent quality and dimensional accuracy. However, the high-speed machining process is not suitable for the rapid realization of 3D-shaped product because a considerable amount of time is required for the work piece fixturing process. High-speed rapid prototyping (HisRP), a new type of RPM technology, will be presented in this paper. The proposed HisRP has been developed using a combination of a multi-face high-speed machining process and a flexible fixturing technique. Low melting point metal alloys are used to hold the work piece during multi-face machining. An automatic set-up device, mounted and fixed to the work table, has also been developed to guarantee positional accuracy during a series of multi-face machining operations. This set-up device is expected to be beneficial for successive multi-face high-speed machining of working materials, for example for two-face or four-face machining. The proposed HisRP process has been shown to be a useful method for manufacturing 3D metal products with reduced lead time. [ABSTRACT FROM AUTHOR]

CONCURRENT engineering, INDUSTRIAL engineering, RAPID prototyping, MATHEMATICAL optimization, ENGINEERING tolerances, NONLINEAR statistical models, NONLINEAR theories, and MACHINE tools

A new method for optimal concurrent process tolerance is proposed. Information related to process planning is used during the structure design stage of a product. The functional tolerances of the assembly of a product are considered process tolerances. A nonlinear optimal concurrent process tolerance model has been established to minimize the total manufacturing cost with different weight factors for the operations of the product. The constraints include concurrent process tolerance chains, the standard coefficient of process tolerance, and the economical maximum tolerance of the machine tools. In order to obtain optimal process tolerances, a new approach based on grey difference degree is presented in this paper. This approach takes the sequence consisting of the optimal value of every objective as the standard sequence, and that consisting of the actual values as the objective sequence. Thus, grey difference degree is calculated and used as the objective of the function. Finally, a practical example is introduced to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, ENGINEERING design, ENGINEERING models, COMPUTER-aided design, and PRODUCTION engineering

Most rapid prototyping (RP) processes adopt a solid CAD model sliced into thin layers of constant thickness in the building direction. Each cross-sectional layer is successively deposited and, simultaneously, bonded onto the previous layer; eventually the stacked layers form a physical part of the model. A new RP process called the Transfer-type Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-st) has been developed to reduce building time and to improve the surface finish of parts with thick layers and sloping surfaces. The objective of this study is to develop a method for calculating the rotation angles (θx, θy) of a linear hotwire cutter in the three-dimensional space for the VLM-st process using inverse kinematics. The method for calculating the rotation angles (θx, θy) of the four-axis hotwire cutter to VLM-st was applied and verified for a variety of free surface bodies. [ABSTRACT FROM AUTHOR]

REVERSE engineering, STATISTICAL sampling, COMPUTER-aided design, THREE-dimensional imaging, OPTOELECTRONIC devices, and PROTOTYPES

The process of capturing the shapes of objects through surface data sampling and generating a 3D CAD model is termed reverse engineering (RE) because the process is the reverse of the normal design and manufacturing sequence. The digitisation process can be achieved through spatial measurements taken by a coordinate measuring machine (CMM). The way of capturing data in a CMM can be divided into contact or non-contact methods. Diode-lasers or CCD cameras are commonly applied in non-contact measuring, while touch probes are applied in contact measuring. There are limitations in obtaining data for complex objects (for under-cut or inner structures) by means of the two abovementioned methods. Therefore, we have designed and assembled a novel device, called an abrasive computed tomography (ACT) apparatus, to overcome the abovementioned limitations. The ACT apparatus uses an abrasive method to remove the inlaid object layer by layer and to capture the cross-sectional image of each layer with a CCD camera. A numerical scheme is applied to obtain the Bezier curve of the boundary in each layer. The combination of all cross-sectional boundaries is used to reconstruct the 3D CAD model of the object. The 3D CAD model can then be transmitted to generate the tool paths in a CNC machine or produce rapid prototyping in a RP machine. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, RAPID prototyping, JOB analysis, TRIANGULATION, ASSEMBLY line methods, and LASERS

The objective of this research is to investigate the effect of slice thickness on the profile accuracy of the model maker (MM) rapid prototyping (RP) system, layer by layer, through non-contact laser probe measurement. A circular triangulation laser probe, model OTM-3A20, made by Wolf & Beck Co., was mounted on a coordinate measuring machine (CMM), as the non-contact sensor. An adjustment device for the laser probe was designed to minimise the cosine error caused by assembly inaccuracy. The alignment test of the measuring laser beam was carried out using a calibrated specimen. The systematic accuracy of the circular triangulation laser probe with respect to the surface roughness and the surface slope of the RP workpiece was investigated using a HP5529A laser interferometer system. The maximum error of 21/2D RP part profile accuracy can be improved from 220 μm to 131 μm, and the average error can be improved from 78 μm to 46 μm as the slice thickness changed from 0.127 mm (0.005 in.) to 0.0127 μm (0.0005 in). However, the machining time increases by about seven fold based on the experimental results. An overall error of 197 μm as measured by the laser probe is attainable using the finest slice thickness 0.0127 mm (0.0005 in.) for the 3D profile accuracy. To verify the accuracy of non-contact laser probe measurement, the 3D profile of the RP part was also measured by a CNC CMM, with good consistency. [ABSTRACT FROM AUTHOR]

CONCURRENT engineering, COMPUTER-aided design, PROTOTYPES, MANUFACTURING processes, SOLID state physics, and NEW product development

Adaptive slicing varies layer thickness by taking the geometry change of the CAD model in the build direction into account to improve surface finish. Direct slicing generates exact slice contours from the original CAD model and avoids an intermediate representation, known as an “STL file”. At present, most direct slicing approaches are restricted to some CSG solids or some CAD systems. In this paper, an approach toward adaptive direct slicing with non-uniform cusp heights independent of CAD systems for rapid prototyping is presented. First the geometry model is imported into the adaptive direct slicing system from CAD systems using the standard STEP format. Using OpenGL graphics libraries, the solid model is then displayed and the user is prompted to specify the allowable cusp height for each highlighted surface. Lastly, the CAD model is sliced adaptively with different cusp heights (tolerance requirements) for different surfaces. With non-uniform cusp heights, adaptive slicing has a higher efficiency. Implementation details and results are also presented. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, CONCURRENT engineering, SILICONE rubber, METHODS engineering, METAL castings, and PRODUCTION planning

Investment casting (IC) offers an economical method for mass producing complex, shaped metal parts. However, high tooling cost and lead times associated with the fabrication of metal moulds for producing IC wax (sacrificial) patterns result in cost justification problems for customised single casting, small- and medium-quantity production. Rapid prototyping (RP) techniques can reduce the costs associated with single-part or small-quantity production as they can be applied to the fabrication of sacrificial IC patterns containing complex and intricate designs with significant cost and lead-time savings. In this project, a benchmark model is designed to assess the fused deposition modelling (FDM) process for creating sacrificial IC patterns. In addition, an indirect approach toward producing wax patterns via silicone rubber moulding is investigated. Cost and lead time comparisons between the two IC pattern production methods were carried out and presented. The dimensional accuracies of metal castings generated from the RP-produced patterns are also presented. [ABSTRACT FROM AUTHOR]

ELECTRODES, PROTOTYPES, INDUSTRIAL design, POWDER metallurgy, MANUFACTURING processes, and COPPER

This paper describes a collaborative research programme aimed at investigating the use of quick EDM electrodes obtained via appropriate rapid prototyping techniques in finishing laser-sintered tools. Two methods were employed in obtaining the EDM electrodes: copper coating of stereolithography models and copper coating of direct metal laser sintered (bronze) models. The amount of copper deposited on both electrode models proved problematic as the electroplating process was unable to deposit enough copper in the inner cavities of the electrodes, with very gradual reduction in copper layer thickness from the outer faces/surface to virtually no deposition in the inner walls and bottom face. Consequently, the electrodes were not suitable for the envisaged EDM process. [ABSTRACT FROM AUTHOR]

RAPID prototyping, SPRAYING, COATING processes, NEW product development, COMPUTER-aided design, and CONCURRENT engineering

Rapid prototyping processes produce parts layer by layer directly from 3D CAD models. An important technique is required to slice the geometric model of a part into layers and to generate a motion code of the cross-sectional contour. Several slicing methods are available, such as slicing from sterolithgraphy (STL) files, tolerate-error slicing, adaptive slicing, direct slicing, and, adaptive and direct slicing. This paper proposes direct slicing from 3D CAD models and generating a G-code contour of each layer using PowerSOLUTION software (Delcam International, Birmingham, UK). PowerSOLUTION includes two main modules: PowerSHAPE is used to build 3D CAD models and PowerMILL is used to produce G-Code tool paths. It provides macro language, picture files and cutting paths for secondary development work. The authors used macro commands to write an interface generating direct slicing from 3D CAD models and G-code contours for all layers. Most well-known controllers in the market accept the G-Code. Therefore, it is easier to apply this scheme in a CNC-machining center to produce rapid prototyping such as laminated object manufacturing (LOM) for complex geometries. The interface was successfully applied the interface to the UV resin spray rapid prototyping (UVRS-RP) machine that was developed to produce RP. [ABSTRACT FROM AUTHOR]

SPRAY nozzles, PROTOTYPES, COMPUTER-aided design, ALGORITHMS, MODELS & modelmaking, and ATOMIZERS

This study aims to build a triangular-mesh model directly from scanned 3D data points, which then generate the stereolithography (STL) file, thus avoiding the troublesome task of producing a CAD model. Accuracy of the triangular-mesh model is achieved because the pitch between data points is generally very small. In addition, the paper proposes a multi-nozzle path algorithm to increase both spraying efficiency and part accuracy. The processing procedure includes: (1) Establishing the triangular-mesh model from scanned data points, which are retrieved by means of contact- or non-contact type measuring machines as well as developing the algorithm to add the radius of the probe automatically. (2) Equally slicing the triangular-mesh solid model and plan spraying paths. (3) Determining the amount and diameter of nozzles appropriate for each slice to generate multi-nozzle spraying paths. [ABSTRACT FROM AUTHOR]

METAL spraying, SHEET metal work, RAPID prototyping, ZINC, PROTOTYPES, and METAL coating

This paper introduces a new sheet metal dieless forming technology. This technology adopts the principle of “layered manufacture” in rapid prototyping technology; it can form sheet metal parts without dies. A new method of tool-path generation based on STL file for sheet metal dieless forming is proposed. [ABSTRACT FROM AUTHOR]

RAPID tooling, METAL spraying, SURFACE hardening, RAPID prototyping, METAL coating, and PROTOTYPES

Repetitively prototyping several prototypes of the same component using currently available rapid-prototyping equipment can be very costly. Substantial savings can be attained with the use of a metal spray process to produce a crust shell on a rapid-prototyping pattern coated with mould release agent (PVA), and then backing the crust with aluminium granules so as to form rapid mould/tooling (RT). The smoothness of the innermost spray layer and its dimensional accuracy in relation to the RP prototype are factors that ensure good quality of parts replicated by RT. This paper establishes a preliminary model for predicting the upper bound of the former and the lower bound of the latter, which have been experimentally verified by arc spraying zinc onto PVA. The theoretical model permits the prediction of spraying parameters for controlling the achievable surface finishing and dimensional accuracy of a spray in RT production. [ABSTRACT FROM AUTHOR]

ALGORITHMS, SCANNING systems, COMPUTER input-output equipment, OPTICS, TRIANGULATION, and GEODESY

For the current generation of rapid-prototyping models, laser scanners are currently being used more frequently due to rapid first measuring speed and high precision. Direct generation of an STL file from the digitised points has a great of advantage in that it can reduce time and error during the modelling process. A reduction in the number of point data is important while generating the STL file directly from the measured point data and maintaining precision. A new approach is developed in this paper to generate an STL file directly from point clouds by indicating a tolerance ε to maintain precision. The STL file can be generated directly from scattered points using a new algorithm that reduces and triangulates digitised point data based on triangulation of 3D parametric surfaces. Two experimental examples are presented to demonstrate the effectiveness and efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, MANUFACTURING processes, LASERS, NEW product development, and INDUSTRIAL design

With the development and refinement of Rapid Prototyping technologies, a gradual move into tooling applications has occurred. However, the design principles that are traditionally applied to mould tools are not always suitable for use with layer-manufactured tools. As these technologies develop, so must the ways in which they are used. Tools produced using Direct Metal Laser Sintering (DMLS) have previously been shown to be suitable for several applications, in particular for plastic injection moulding. However, there has been little work undertaken on the best procedures to follow when designing tools made using the DMLS process. This work has been performed to determine the effect of layer thickness, level of finishing and draft angle on the forces required to eject parts from DMLS injection mould tools. Results show that, although the choice of layer thickness and the level of tool finishing have a substantial effect on the ejection forces required, the level of draft included does not show an obvious trend towards increasing or decreasing the force. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MATERIALS, PROTOTYPES, CONCURRENT engineering, HARD materials, STRENGTH of materials, and MANUFACTURING processes

Slicing is a fundamental process planning task and an important procedure in rapid prototyping. However, most research currently focuses on the slicing of homogeneous objects and few approaches for slicing of heterogeneous objects have been reported in the literature. In this article, we present an approach for adaptive slicing of functionally graded material objects. Unlike homogeneous objects, functionally graded material objects contain both geometry and material information. The layer thickness is computed by considering not only geometry but also material variation along the build direction. The continuous material distribution in each layer is discretised into step-wise gradings by subdividing the slice into sub-regions, which can be regarded as homogeneous material regions. An algorithm that summarised the slicing procedure is described and an example is also presented. [ABSTRACT FROM AUTHOR]

PROTOTYPES, METALS, CERAMICS, SLURRY, ENGINE cylinders, and COMPUTER-aided design

The dimensional accuracy and surface finish of ice patterns generated by rapid freeze prototyping were first investigated. The dimensional accuracy and surface finish of metal parts made by investment casting with ice patterns were then investigated and compared with those made by conventional investment casting with wax patterns. The selection of binder, ceramic powder, and catalyst material for ceramic slurries in the process of investment casting with ice patterns and the need for an interface agent to separate the ice pattern from the ceramic slurry in the mold making process are discussed. The parts used in the investigation included circular cylinders with vertical and slant walls and a turbine impeller. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MANUFACTURING processes, PROTOTYPES, NEW product development, BIOMEDICAL materials, and CONCURRENT engineering

In this paper, a novel method for reconstructing and fabricating a missing ear is presented based on rapid prototyping (RP) and the FreeForm modelling system. Using the method, the image of the normal ear is extracted, mirrored, and positioned onto the image of the deformed side of the face precisely, and the undersurface of the ear prosthesis can match the remnant tissue of deformed side perfectly without making a wax ear. In the clinic, six ear prostheses have been produced and applied successfully. The results suggest that high accuracy has been achieved in shape, size, and protrusion of the ear prostheses, which indicates that the application of RP techniques in conjunction with the FreeForm modelling system is a suitable approach for fabricating ear prosthesis. [ABSTRACT FROM AUTHOR]

METAL castings, MANUFACTURING processes, PROTOTYPES, INVESTMENTS, PRODUCTION engineering, NEW product development, FEASIBILITY studies, and SILICONE rubber

Although investment casting (IC) provides an economical method for the mass production of metal parts with complex and intricate features, the relatively long lead times and high tooling costs involved in the manufacture of metal moulds for the fabrication of sacrificial IC wax patterns lead to cost justification problems for customised single casting, small and medium quantity production. The application of rapid prototyping (RP) technologies to fabricate complex sacrificial IC patterns can result in significant reduction in the costs and lead times associated with single part or small quantity production. Previously, the authors assessed the suitability of the fused deposition modelling process, in particular ABS models, for creating sacrificial IC patterns [1]. The current research looks into the feasibility of employing patterns fabricated by Model Maker II (MMII) as sacrificial IC patterns to produce metal castings rapidly. In addition, an indirect approach involving the utilisation of silicone rubber moulding with an MMII-fabricated master pattern to produce sacrificial IC wax patterns is investigated. The dimensional accuracies and surface qualities of the final metal castings generated from the RP-produced patterns are presented. Cost and lead time comparisons are also carried out and presented . [ABSTRACT FROM AUTHOR]

LAMINATED materials, TOOLS, NONLINEAR optics, OPTOELECTRONIC devices, NEW product development, MANUFACTURING processes, and PROTOTYPES

Laminate tooling is a relatively fast and simple method of making large metal tools directly for various moulding processes in the rapid prototyping and manufacturing field. Metal sheets are usually cut, stacked, aligned and joined. In most cases, lasers are used only for the cutting of steel sheets in laminate tooling, but in this study, the use of the laser was expanded for improved laminate tooling. First, the laser was applied to eliminate the stair steps of steel laminates by filling them with molten filler metals. Then application of hard particles to molten filler metals for improved surface hardness of laminate tools was investigated. To achieve this goal, a CO2 laser system composed of a CO2 laser, a five-axis CNC table, an automatic feeding equipment of filler metal and flux and a personal computer was developed. Various experiments on filling stair steps and hardening were performed and the results were verified and estimated. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MANUFACTURING processes, PROTOTYPES, PRODUCTION (Economic theory), and PRODUCTION engineering

Investment casting (IC) has benefited numerous industries as an economical means for mass producing quality near net shape metal parts with high geometric complexity and acceptable tolerances. The economic benefits of IC are limited to mass production. The high costs and long lead-time associated with the development of hard tooling for wax pattern moulding renders IC uneconomical for low-volume production. The outstanding manufacturing capabilities of rapid prototyping (RP) and rapid tooling (RT) technologies (RP&T) are exploited to provide cost-effective solutions for low-volume IC runs. RP parts substitute traditional wax patterns for IC or serve as production moulds for wax injection moulding. This paper reviews the application and potential application of state-of-the-art RP&T techniques in IC. The techniques are examined by introducing their concepts, strengths and weaknesses. Related research carried out worldwide by different organisations and academic institutions are discussed. [ABSTRACT FROM AUTHOR]

METAL powders, STEEL, ATOMIZATION, LASERS, MATERIALS, MANUFACTURING processes, and TOOLS

To date only gas-atomised tool steel powders have been used for direct laser additive manufacturing and the potential benefits of using water-atomised powders have not been explored. As the use of the process in the rapid tooling field is growing, there is a need to explore if the less expensive water-atomised materials can be realistically utilised. A comparative investigation is described, using gas- and water-atomised H13 powder deposited with a CO2 laser and coaxial powder feed nozzle. Multiple layer wall dimensions, composition, microstructure, surface finish and hardness are related to process conditions and the causes of the observed phenomena are discussed. An energy-balance method is used to model the temperature of the powders and the results used to explain some of the effects. Results indicate that using the lower cost water-atomised powder still allows a metallurgically sound component to be built and does not significantly affect surface finish. The build rate is, however, lower and the water-atomised powder tends to produce slightly softer walls, attributable to a higher temperature during tempering of deposited material by subsequent laser passes. [ABSTRACT FROM AUTHOR]

RAPID prototyping, MANUFACTURING processes, NEW product development, PRODUCT management, ALUMINUM, ELECTRONIC industries, and INDUSTRIAL engineering

Rapid prototyping (RP) has already proven itself in the electronics industry as a method for shortening the product development time cycle. In the development of the optical pickup unit (OPU), extremely high precision is needed to make a functional model. Very often, in the design phase of the product development cycle, the prototype of the OPU is machined from a single piece of aluminium block to make the working sample. In this project, a comparison of the machined aluminium sample, RP samples from various RP processes and that moulded out from the injection moulding machine is made on surface finishing as well as dimensional accuracy. Finally, a comparison of tooling cost, piece part cost and lead time of obtaining the parts is also discussed on the different prototyping and manufacturing processes. [ABSTRACT FROM AUTHOR]

ISOSTATIC pressing, PROTOTYPES, COMPUTER-aided design, ALGORITHMS, RAPID prototyping, and LASERS

A CAD application tool kit interfacing with a Unigraphics (UG) system was developed for disintegrating large and complex rapid prototyping objects into smaller and simpler components which can be fabricated by a rapid prototyping system. As the core of the tool kit, the algorithm of such disintegration is described in detail in this paper. The algorithm combines the flat planar parting method and feature-based volume decomposition. Due consideration is also given to the optimisation of the surface accuracy, the build time, and the strength and number of segments generated. Based on the algorithm and the CAD application tool kit, the disintegration of two RP objects was realised in a selective laser sintering system. [ABSTRACT FROM AUTHOR]

AUTOMOTIVE engineering, PRODUCT management, COST effectiveness, RAPID prototyping, COMPUTER simulation, and NUMERICAL analysis

Taking automobile design as a study case, this paper presents the approaches to implement a distributed image-based virtual prototyping (VP) system employing distributed virtual reality (DVR) technology combined with image-based rendering (IBR) technology. Firstly, the methods to implement an image-based closed spherical space are presented, which can be used to construct a photo-quality virtual prototype; secondly, the novel vision sensitivity-based rendering tactic and the relevant image cubic-spline interpolation methods, which visibly improve the efficiency of rendering, is represented. Finally, a distributed image-based virtual prototyping system is implemented, by which a product designer can easily and rapidly construct a photo-quality virtual prototype and distribute it on the Internet, whereby buyers can visually understand whether or not the product can meet their individual requirements. This system enables buyers and designers to visually evaluate and discuss the design remotely, which has consequently improved the design efficiency greatly and lowered the cost substantially. [ABSTRACT FROM AUTHOR]

SOLID freeform fabrication, RAPID prototyping, MACHINING, INDUSTRIAL lasers, and MICROMACHINING

Solid freeform fabrication has attracted considerable attention lately because of its ability to build a 3D structure with a complex and arbitrary shape. This work presents initial studies to adapt this technology for the fabrication of meso-/micro-3D structures. A pulsed Nd:YAG laser was used for laser microdeposition (additive) and micromachining (subtractive) processes. An ultrasonic-based micropowder feeding system was developed to generate precise patterns of micropowders on a substrate without any pre-processing. Laser microdeposition of copper and stainless steel micropowders was accomplished. The characterization of micromachining was performed on stainless steel and copper plates with a laser beam of wavelengths of 355 nm and 266 nm. The integration of laser microdeposition and micromachining processes improved the resolution and edge quality of the meso-/micropatterns. [ABSTRACT FROM AUTHOR]

REVERSE engineering, QUALITY control, PRODUCT quality, TOTAL quality management, and MANUFACTURING processes

Quick error comparisons of fabricated parts and an original CAD design is often a difficult yet important issue in product quality control. In this paper we present an integrated technique of 3D scanning with reverse engineering and rapid prototyping technologies. This will be applied to the entire quality control phase of quick response products during the manufacturing process. By using 3D scanning and reverse engineering technology in conjunction with rapid prototyping technology, the geometric data of components can be easily and rapidly measured and analyzed. The detailed report can be printed out directly to fulfill the requirement of total quality control for quick response products. The proposed technique is especially suitable for fragile or soft material made products, like thin shell or rubber parts. With its accuracy and ease of operation, this integrated method is able to help manufacturers improve their global competitiveness in the 21st century. [ABSTRACT FROM AUTHOR]

DECISION support systems, RAPID prototyping, COMPUTER-aided design, NEW product development, and INDUSTRIAL costs

As a new technology that fabricates a three-dimensional (3D) physical model from computer-aided design (CAD) data using an additive process, rapid prototyping (RP) has been developed to reduce product development time and cost. Recently, many newly emerging techniques of RP have been commercialized worldwide. This paper deals with the selection of an optimal RP system that best suits the end use of a part by using multiple-attribute decision making and the test part designed with conjoint analysis to reflect users’ preference. Evaluation factors include only the major attributes that significantly affect the performance of an RP system such as accuracy, roughness, strength, elongation, part cost and build time. Crisp values such as accuracy and surface roughness are obtained with a new test part developed in this study. The part cost and build time are identified as falling within approximate ranges due to varying costs and many variable parameters. They are presented as linguistic values that can be described with triangular fuzzy numbers. Based on the evaluation values obtained, an appropriate RP process for a specific part application can be selected using a modified technique of order preference by a similarity to ideal solution (TOPIS) method given crisp data and linguistic variables as the alternatives of attributes. Finally, each attribute’s weight is assigned using a pairwise comparison matrix. Determined using these weights, the final ranking order aids in the selection of the RP system. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, RAPID prototyping, SCANNING systems, GALVANOMETER, ALGORITHMS, and LASERS

The laser galvanometric scanning technique has brought rapid prototyping manufacturing into a new era. However, a number of errors severely affect the prototyping accuracy of the work piece. This paper gives a detailed analysis of the errors involved in the galvanometric scanning system used in rapid prototyping manufacturing. A positional correction algorithm has been developed to rectify the errors to meet the precision requirements of the processing. Experimental results based on a selective laser stinting (SLS) machine prove the efficiency of the positional correction algorithm. [ABSTRACT FROM AUTHOR]

ENGINEERING, OPTICS, REVERSE engineering, SURFACES (Technology), and APPLICATION software

The use of OPL-3D, a robust, flexible and easy-to-use optical digitizer, in conjunction with reverse engineering procedures is presented. The optical digitizer is used as a stand-alone (i.e., not in tandem with popular CMM’s) system, whose output point clouds can be manipulated, by means of both specifically-designed software and high-performance commercial software, to produce mesh surfaces and NURBS of the acquired shape. The digitizer-process combination yields accurate digital replicas of the target object, the accuracy of the whole combination being on the order of 1/1500 of the measurement range. The speed of acquisition, combined with the above high accuracy, the ease of use and the fact that recalibration is seldom required makes the digitizer ideal for reverse engineering in an enormous number of applications ranging from automotive to biomedical. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, LASER beams, MACHINING, MACHINE-shop practice, PRODUCT quality, and RESEARCH

Two sets of optical sources with different laser beam diameter are integrated into a rapid prototyping system for increased machining speed in this research. The smaller laser beam is used to scan the object contour to obtain an accurate machining surface and the larger laser beam is used to quickly scan the inner part of the contour without precision control limitation to save machining time. The fabrication parameters of this system are investigated based on product quality and accuracy of practical implementations. The path planning of the inner part and the outer contour are discussed. The user-friendly man-machine interface is developed using the Visual Basic program . [ABSTRACT FROM AUTHOR]

PARAMETRIC devices, RAPID prototyping, AUTOMATION, MANUFACTURING processes, and PROTOTYPES

Parametric modeling technology is difficult to apply to freeform mesh models since there is no efficient way to impose geometric constraints. In this paper, we propose a novel method to control freeform mesh models parametrically. Our approach is to construct a control mesh that surrounds an object model and then impose constraints on it. The control mesh is parametrically controlled and the shape of the object model is modified by using an existing freeform deformation method. This paper is mainly concerned with automated construction of a control mesh and treatment of geometric constraints. Procedures for creating a control mesh are as follows: 1) determine the optimal orientation of the model, 2) project the model along three axes and extract contours, 3) create 2D control polygons for the contours, and 4) construct the 3D control mesh from the 2D control polygons. Geometric constraints are imposed on the edges and faces of a control mesh. Types of constraints are given by either a relative relationship between elements or an absolute displacement. A new control mesh is calculated by solving these constraints and the original model is modified accordingly. We tested our algorithms for two freeform models. [ABSTRACT FROM AUTHOR]

POROUS materials, RAPID prototyping, PROTOTYPES, TISSUE engineering, and MANUFACTURING processes

This research paper addresses the issue of developing an efficient methodology to design and manufacture a complex scaffold structure of desired porosity required for tissue engineering applications using a novel approach based on fused deposition modelling (FDM) rapid prototyping (RP) technology. The scaffold provides a temporary biomechanical structure for cell growth and proliferation to produce the required body parts. Conventional techniques of scaffold fabrication (such as fibre bonding, solvent casting and melt moulding) generate scaffolds with unpredictable pore sizes due to their limitations in flexibility and control of pore volume and distribution. Moreover, such scaffolds have poor mechanical strength and structural stability. The paper describes an FDM pre-processor that ensures the fabrication of scaffolds of desired porosity and inter-connectivity on the FDM system. [ABSTRACT FROM AUTHOR]

LAMINATED materials, MANUFACTURING industries, HEATING, HEAT transfer, FINITE element method, ANSYS (Computer system), and COMPUTER programming

To improve the hot-pressing process currently employed in laminated object manufacturing (LOM), an innovative heating-and-pressing separation system is proposed, and heat transfer problems of this system are investigated. A thermal model is first established. It is solved numerically by the finite element method (FEM) software ANSYS, and verified by experiments. Based on the numerical solution under various operating conditions, it is found that the operating temperature of an adhesive can be reached quickly when the heater is maintained at a higher temperature, corresponding to a deeper heat-affected zone. This shortcoming can be effectively reduced if the speed of the heater is increased. Hence, a higher heater temperature together with a higher moving speed is suggested to shorten processing time and promote manufacturing efficiency. Through analysis, the appropriate distance between the roller and the heater, so as to obtain finished parts of high quality, is determined. [ABSTRACT FROM AUTHOR]

MANUFACTURING processes, RAPID prototyping, HIGH-speed machining, REVERSE engineering, AEROSPACE industries, and INDUSTRIAL costs

This paper presents a comprehensive set of theoretical investigations and industrial applications of computer-based rapid manufacturing technology for high-integrity aerospace components. Two rapid manufacturing processes have been proposed by integrating rapid prototyping, high-speed machining (HSM), reverse engineering and geometric computation theory. They have been validated through trial manufacturing of a matrix of current aerospace components embracing critical design features to be found across the aerospace industry. Applied to future development programmes, this research will provide aerospace companies the benefits of significant decrease in product introduction lead-time, savings in non-recurring product introduction costs and considerable reduction in manufacturing costs for “one off” and low volume service parts. The findings can also be applied to rapid prototype development in other industries, such as automotive and military. [ABSTRACT FROM AUTHOR]

SURFACES (Technology), RAPID prototyping, MACHINING, MANUFACTURING processes, REVERSE engineering, and SPLINE theory

The issue of surface reconstruction and slicing from point clouds has been receiving extensive attention recently. When using the B-spline surface fitting technique, the difficulty of parameterization exists. At the same time, for interfacing between reverse engineering and rapid prototyping, the point clouds are usually converted to an stereolithography (STL) model. This leads to a huge file size and requires expert modeling skills. The objective of this work is to establish a base surface parameterization and direct slicing strategy for scattered data based on a cross-sectional design technique. We first present a new method of directly extracting sectional contours from point clouds. Then, we create a base surface by skinning the primary boundary curves and interior sectional curves. Based on a good parameterization, the final surface is achieved with tight tolerance. Several practical examples have demonstrated the feasibility of the proposed method. It can be widely used in Number Control (NC) machining and rapid prototyping. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, INDUSTRIAL design, ENGINEERING design, and ENGINEERING models

The rapid prototyping (RP) process is the fastest and most feasible method for prototype construction. However, with the use of any material or build method the phenomenon of volume shrinkage is unavoidable. It is known that volume shrinkage and curl distortion are the major causes that lead to poor accuracy of the built prototype. Subsequently, in order to improve the precision of dimension and volume shrinkage, more expensive equipment is used on the market. Also, it is expensive and inefficient to obtain better process parameters through trail and error in the RP process. In order to improve the precision of dimension, reduce the processing cost and the frequency of trail and error, this study first induces the concept of computer-aided engineering (CAE) into the processing of RP, which uses a dynamic finite element simulation code to simulate the photopolymerization process, so as to reduce the time for selecting the processing parameters and obtain the distortion data. Second, by means of reverse distortion compensation to obtain a new CAD model, then it is sent to a RP machine for the actual prototyping processes, so as to obtain a more accurate precision. Finally, in order to confirm this method and restriction in experimental equipment, the stereolithography process and simple laser scanning path are chosen as examples. The results of the simulation and experiment prove that the method proposed herein is effective. It not only can reduce the cost of equipment but also obtain a better precision of dimension on final-parts at the same time. Besides, it is believed that this research method can be promoted to other materials or build methods in RP fabrication . [ABSTRACT FROM AUTHOR]

INJECTION molding of metals, RAPID prototyping, PRODUCTION planning, COST control, PRODUCTION engineering, and MANUFACTURING processes

Functional parts are needed for design verification testing, field trials, customer evaluation, and production planning. By eliminating multiple steps, the creation of the injection mold directly by a rapid prototyping (RP) process holds the best promise of reducing the time and cost needed to mold low-volume quantities of parts. The potential of this integration of injection molding with RP has been demonstrated many times. What is missing is the fundamental understanding of how the modifications to the mold material and RP manufacturing process impact both the mold design and the injection molding process. In addition, numerical simulation techniques have now become helpful tools of mold designers and process engineers for traditional injection molding. But all current simulation packages for conventional injection molding are no longer applicable to this new type of injection molds, mainly because the property of the mold material changes greatly. In this paper, an integrated approach to accomplish a numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. Comparisons with experimental results are employed for verification, which show that the present scheme is well suited to handle RP fabricated stereolithography (SL) molds. [ABSTRACT FROM AUTHOR]

METALWORKING industries, METALWORK, RAPID prototyping, PROTOTYPES, MANUFACTURING processes, and FINITE element method

This paper develops a FORTRAN program to convert the explicit dynamic finite element method (FEM)-simulated deformed sheet to the stereolithography (STL) format used in the rapid prototyping (RP) apparatus. Such integration of the RP/FEM can rapidly produce a visualized 3D physical part of the sheet deformation state. Three cases – cylindrical drawing, bore expanding and square cup drawing processes, simulated by explicit dynamic FEM – were investigated to verify the integration system. The wrinkled flange in the cylindrical drawing process, the circle hole expansion in the bore expanding process, and the square cup in the square cup drawing were successfully predicted by explicit dynamic FEM, and the rapid prototyping 3D physical parts also showed good visualization of the deformed sheet for the above three cases. It proves that the integration system of RP/FEM will be able to supply a useful method for the visualization of the 3D physical part in the sheet metal forming process. [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, MANUFACTURING processes, FINITE element method, and PROSTHETICS

This paper presents a non-uniform, periodic closed B-spline approximation algorithm for the fabrication of a medical pelvic model, based on rapid prototyping, and also gives the finite element evaluation of the pelvic model. Rapid prototyping (RP), when used in fabricating medical prosthesis, has a strict requirement for closeness and impermeability of STL files. Incorrect data structure in STL files will cause the subsequent slicing process not to proceed. The non-uniform periodic closed B-spline curve approximation method was applied to processing CT data. The precision and size of STL files was improved to optimize the RP model of the pelvis. Finally, the model of the pelvis was evaluated with the finite element method. Results suggest that a high similarity has been achieved in terms of shape, size and biomechanical properties of the pelvic model and the normal one, which validates our argument that rapid prototyping with non-uniform, periodic closed B-spline algorithm is suitable for the fabrication of a pelvic model, which will prove to be significant in the design of pelvic prostheses . [ABSTRACT FROM AUTHOR]

RAPID prototyping, PROTOTYPES, INDUSTRIAL design, ENGINEERING design, MANUFACTURING processes, and INDUSTRIAL engineering

Several important factors must be taken into consideration in order to maximize the efficiency of rapid prototyping (RP) processes. The ability to select the optimal orientation of the build direction is one of the most critical factors in using RP processes, since it affects part quality, build time, and part cost. This study aims to determine the optimal build-up direction when a part is built with the variable layer thickness for different RP systems. The average weighted surface roughness (AWSR) that is generated from the stair stepping effect, the build time, and the part cost using the variable layer thickness are all considered in the process. Using the multi-attribute decision-making method, the best orientation is determined among the orientation candidates chosen from the convex hull of a model. The validity of the algorithm is illustrated by an example. The algorithm can help RP users select the best build-up direction of the part and create an efficient process planning. [ABSTRACT FROM AUTHOR]

COMPUTER integrated manufacturing systems, DATA mining, DATABASE searching, KNOWLEDGE management, ALGORITHMS, MANUFACTURING processes, and AUTOMATION

In this paper, a new data mining algorithm based on the rough sets theory is presented for manufacturing process control. The algorithm extracts useful knowledge from large data sets obtained from manufacturing processes and represents this knowledge using “if/then” decision rules. Application of the data mining algorithm developed in this paper is illustrated with an industrial example of rapid tool making (RTM). RTM is a technology that adopts rapid prototyping (RP) techniques, such as spray forming, and applies them to tool and die making. A detailed discussion on how to control the output of the manufacturing process using the results obtained from the data mining algorithm is also presented. Compared to other data mining methods, such decision trees and neural networks, the advantage of the proposed approach is its accuracy, computational efficiency, and ease of use. [ABSTRACT FROM AUTHOR]

ARTIFICIAL implants, BIOMEDICAL materials, DIAGNOSTIC imaging, MEDICAL imaging systems, DESIGN, and SURGEONS

The conventional design process is prior to surgical interventions. The accuracy and efficiency of this method is heavily dependent on experiences and skills of the designer. In order to decrease the dependence on design experience and enhance the participation of surgeons in the design process, we developed a novel method to design and fabricate customized exact-fit medical implant. This method involves several technologies such as three-dimensional geometry modeling based on sectional medical images, triangular mesh defragmentation and rapid (RP) prototyping technology. With the help of a three-dimensional triangular mesh model and RP model, surgeons and engineers could consult conveniently over the design process and modify the design to achieve an exact-fit implant. The result indicates that by using this method the accuracy and efficiency is improved greatly. [ABSTRACT FROM AUTHOR]

PERIODONTAL splints, PERIODONTAL prosthesis, SIMULATION methods & models, RAPID prototyping, PROTOTYPES, and MANUFACTURING processes

The conventional design and fabrication of dental splints (in orthognathic surgery) is handmade through the two-dimensional preoperative planning and model surgery. The accuracy and efficiency of this method is not satisfactory. In order to solve the problems and exploit the trend of computer-assisted surgery, we developed a novel method to design and fabricate a computer-generated dental splint, which is based on three-dimensional model simulation and rapid prototyping technology. After surgical planning and simulation of the 3D model, we optimize the model with respect to both the chewing action (functional) and overall facial appearance (aesthetic). Then, through a Boolean operation of the splint blank and the maxilla-mandibula model, the dental splint model is formed. Finally, this model is fabricated by a rapid prototyping system and applied in a clinical setting. The results show that by using this method, the accuracy and efficiency are improved greatly. [ABSTRACT FROM AUTHOR]

PLASTER, FOUNDING, DIE castings, RAPID tooling, MANUFACTURING processes, RAPID prototyping, and VIBRATION (Mechanics)

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties. [ABSTRACT FROM AUTHOR]

PRODUCTION engineering, CONCURRENT engineering, INDUSTRIAL engineering, RAPID prototyping, MANUFACTURING processes, and REPETITIVE manufacturing systems

In the traditional process of designing a manufacturing system, a sequential approach treats each of the design steps individually, without considering the requirements of concurrent design activities. The lack of systematic and concurrent consideration of the interactive impact of design decisions leads to repeated and excessive changes in the design and process. To resolve this problem, this research develops a production engineering-oriented virtual factory – a planning cell-based manufacturing systems design approach. The manufacturing systems design process based on a planning cell is reengineered according to the concept of concurrent engineering. The process modeling of a production engineering-oriented virtual factory is proposed at generic and particular levels. An illustrative example of an engine assembly plant demonstrates the effectiveness of the new approach. [ABSTRACT FROM AUTHOR]

MEDICAL imaging systems, SIGNAL-to-noise ratio, TOPOLOGY, SURFACE roughness, RAPID prototyping, and DIAGNOSTIC imaging

Isosurface generation from medical images was done using an oversampling method. The key idea of the proposed method was based on the fact that oversampling and downsampling together can improve the signal-to-noise (SNR) ratio. The procedure consisted of four phases: (1) oversampling of a voxel, (2) topology estimation, (3) low-pass filtering, and (4) downsampling. The effectiveness of the method was verified in terms of SNR, compactness, and surface roughness of the fabricated rapid prototyping parts. [ABSTRACT FROM AUTHOR]

SINTERING, RAPID tooling, MANUFACTURING processes, MACHINING, and POWDER metallurgy

Prototype injection moulds for plastic parts must face two constraints: be designed and manufactured as quickly as possible and have a short lead time. Moreover, moulds have to evolve in the same way as the part does, to provide either a new functionality or a variant of this part. The current approach is based on a multi component tooling (hybrid rapid tooling) in order to more easily manufacture each component of the mould and to have a greater reactivity to each product evolution. In this paper, we propose a method to manufacture the mould in multi components. This approach is based on process capability criteria (i.e. topological and geometrical criteria). An industrial example is presented. We will focus on the choice between three processes mainly used in hybrid rapid tooling: high speed machining (HSM), electro discharging machining (EDM) and direct metal laser sintering (DMLS). [ABSTRACT FROM AUTHOR]